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Subject[PATCH][next] tty: Avoid the use of one-element arrays
One-element arrays are being deprecated[1]. Replace the one-element arrays
with simple value types 'char reserved_char' and 'compat_int_t reserved'[2],
once it seems these are just placeholders for alignment.

Also, while there, use the preferred form for passing a size of a struct.
The alternative form where struct name is spelled out hurts readability
and introduces an opportunity for a bug when the variable type is changed
but the corresponding sizeof that is passed as argument is not.

Lastly, fix the checkpatch.pl warnings below:

ERROR: code indent should use tabs where possible
+ char reserved_char;$

WARNING: please, no spaces at the start of a line
+ char reserved_char;$

ERROR: code indent should use tabs where possible
+ compat_int_t reserved;$

WARNING: please, no spaces at the start of a line
+ compat_int_t reserved;$

[1] https://github.com/KSPP/linux/issues/79
[2] https://github.com/KSPP/linux/issues/86

Tested-by: kernel test robot <lkp@intel.com>
Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/0-day/tty-20200716.md
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
drivers/tty/tty_io.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 5a6f36b391d9..505bcba5ee02 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2683,7 +2683,7 @@ struct serial_struct32 {
compat_int_t baud_base;
unsigned short close_delay;
char io_type;
- char reserved_char[1];
+ char reserved_char;
compat_int_t hub6;
unsigned short closing_wait; /* time to wait before closing */
unsigned short closing_wait2; /* no longer used... */
@@ -2691,7 +2691,7 @@ struct serial_struct32 {
unsigned short iomem_reg_shift;
unsigned int port_high;
/* compat_ulong_t iomap_base FIXME */
- compat_int_t reserved[1];
+ compat_int_t reserved;
};

static int compat_tty_tiocsserial(struct tty_struct *tty,
@@ -2705,7 +2705,7 @@ static int compat_tty_tiocsserial(struct tty_struct *tty,
struct serial_struct v;
int flags;

- if (copy_from_user(&v32, ss, sizeof(struct serial_struct32)))
+ if (copy_from_user(&v32, ss, sizeof(*ss)))
return -EFAULT;

memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
@@ -2743,7 +2743,7 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
0xfffffff : ptr_to_compat(v.iomem_base);
v32.iomem_reg_shift = v.iomem_reg_shift;
v32.port_high = v.port_high;
- if (copy_to_user(ss, &v32, sizeof(struct serial_struct32)))
+ if (copy_to_user(ss, &v32, sizeof(v32)))
err = -EFAULT;
}
return err;
--
2.27.0
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